Given below are two statements :
Statement $I$ : If $BOD$ is $4\,ppm$ and dissolved oxygen is $8\,ppm$,then it is a good quality water.
Statement $II$ : If the concentration of zinc and nitrate salts are $5\,ppm$ each,then it can be a good quality water.
In the light of the above statements,choose the most appropriate answer from the options given below :

• A
  Both the statements $I$ and $II$ are incorrect
• B
  Statement $I$ is incorrect but Statement $II$ is correct
• C
  Both the statements $I$ and $II$ are correct
• D
  Statement $I$ is correct but Statement $II$ is incorrect